[en] This publication is dealing with determination of levamisole residual amounts in animal origin products with chromatographic and mass spectrometric methods. Mass spectra of levamisole obtained using different ionization methods (EI, PCI, NCI, electrospray) and possible levamisole fragmentation patterns are considered. Optimization of analytical methods for determination of levamisole is performed with regard to achieve the highest sensitivity level of analysis. Main characteristics of the GC/MS EI, PCI and LC/MS/MS methods (linearity, reproducibility) were compared. Possibility of using of gel permeation chromatography and Oasis MCX solid phase extraction procedures for the sample clean-up is described. The presence of levamisole in 7 liver samples (from 140 samples tested) was established. The found concentrations of this potential harmful compound were below the maximum allowed content. (authors)